The volume of a stock is the number of shares traded for a given day. In 2011, Starbucks stock had a mean daily volume of 7.52 million shares according to Yahoo!Finance. A random sample of 40 trading days in 2014 was obtained and the volume of shares traded on those days was recorded. Go to  ww.pearsonhighered.com/sullivanstats to obtain the data file 10_3_25 using the file format of your choice for the version of the text you are using. 

(a) Draw a histogram of the data. Describe the shape of the distribution.

(b) Draw a boxplot of the data. Are there any outliers?

(c) Based on the shape of the histogram and boxplot, explain why a large sample size is necessary to perform inference on the mean using the normal model.

(d) Does the evidence suggest that the volume of Starbucks stock has changed since 2014? Use an a = 0.05 level of significance.